The types of pulmonary ventilation dysfunction are: obstructive ventilation dysfunction, restrictive ventilation dysfunction, and mixed ventilation dysfunction. Obstructive ventilatory dysfunction is characterized by a decrease in flow rate (FEV1.0/FVC%), whereas restrictive ventilatory dysfunction is characterized by a decrease in lung volume (e.g., VC), and mixed dysfunction is a combination of both. The main basis for determining the type of ventilatory dysfunction is the pulmonary function test, which needs to be combined with the clinical data to make a correct conclusion.
The following steps can be followed to analyze the results of pulmonary function tests.
Step 1: FVC
If the FVC is normal, restrictive ventilation dysfunction can be basically excluded. If it is reduced, it is necessary to identify whether it is obstructive or restrictive ventilation dysfunction.
Step 2: FEV1
Normal: It can exclude the obvious restrictive and obstructive ventilation dysfunction.
Decreased: indicates the presence of ventilation dysfunction. Since both restrictive and obstructive ventilation dysfunction can show decreased FEV1, FEV1/FVC needs to be evaluated to determine if obstruction is present. If available, the TLC should be checked; an increase in TLC greater than 15% suggests obstruction; a normal or increased TLC may exclude restriction; a decrease in TLC suggests restriction, and for mixed ventilation dysfunction, the TLC may occasionally be normal.
Step 3: FEV1/FVC
Normal:Obstructive ventilatory dysfunction can usually be ruled out.
A normal or increased FEV1/FVC combined with a decreased FVC often suggests restrictive ventilation dysfunction. If in doubt, TLC or DLCO can be checked, and can be combined with a chest radiograph to check for a basis for reduced TLC.
Reduced FEV1/FVC is highly suggestive of obstructive ventilation dysfunction and is an important indicator of obstructive ventilation dysfunction.
Step 4: Expiratory flow values
FEF25-75 is consistent with the change in FEV1, but is more sensitive.
Step 5: MVV
MVV is generally consistent with changes in FEV1, but is more sensitive. Clinically, MVV values can be calculated from FEV1. Under normal conditions, the expected MVV = FEV1 × 40, and the expected low limit of MVV can be used in clinical work as a basis for determining whether MVV is appropriate. the expected low limit of MVV = FEV1 × 30. if MVV < FEV1 × 30, it often indicates that the patient is not exerting, poor cooperation, fatigue, neuromuscular disorders, etc., and requires careful screening by the technician; if MVV is significantly > FEV1 × 30, it often indicates that the determination of FEV1 30, it often suggests that the determination of FEV1 is not exerted or there is a serious obstructive ventilation dysfunction.
The main reasons for the uncoordinated lowering of MVV and FEV1 are atmospheric airway obstruction or neuromuscular disorders.
Step 6: DLco
A decrease in DLco is indicative of a restrictive lesion of the lung parenchyma. If the decrease is simple, pulmonary vascular disease is most often considered.
Increased, seen in asthma, obesity, alveolar hemorrhage, etc.
Step 7: Bronchial responsiveness measurement